The present invention relates in general to an apparatus for dispensing pesticides, and more particularly to an insect bait station for use with crawling insects.
One of the most popular and effective methods of combating crawling insects is the use of bait which is commonly positioned around or near the insect nest or near where insects gather food. According to their usual food gathering habits, crawling insects will feed on the poisonous bait and take some of the bait with them back to their nests or homes where the bait is shared with other insects, preferably the queen, and as a result, kill a large number of insects.
Various devices typically referred to as insect bait stations have been utilized to present bait to crawling insects, and are well known. Typical insect bait stations have a base with various topographical features used to direct the insects to bait, and a cover that spans those features to create an enclosed bait station. Typical examples of insect bait stations are disclosed in Woodruff et al U.S. Pat. No. 4,563,836; Demarest U.S. Pat. No. 4,837,969; and Demarest et al U.S. Pat. Nos. 5,960,585 and 5,802,761. These and all other patents and publications referred to herein are incorporated herein by reference as if fully set forth. The base of each of the bait stations disclosed in the above patents is formed as a unitary piece of a relatively thin, deformable sheet or film of plastic material that utilizes walls or passageways integrally formed as part of the base to direct insects to the bait. The cover typically spans these structural features without significantly obstructing them.
Woodruff et al U.S. Pat. No. 4,563,836 is an example of this sort of structure. The base of the Woodruff et al bait station includes outer and inner walls with openings in them through which insects can pass. The cover, which spans all of these features formed in the base, is elevated well above the openings formed in the walls which leaves these openings sufficiently unobstructed so an insect can pass through them to the bait.
The bait stations illustrated and described in Demarest U.S. Pat. No. 4,387,969 and Demarest et al U.S. Pat. Nos. 5,906,585 and 5,802,761 utilizes a different approach. In the Demarest patents, the base includes a number of upwardly projecting support features, and the cover provides the exterior sidewalls of the bait station. The cover thus constitutes a shell that fits down over and interacts with the underlying support structures of the base. The doorways by which insects enter the Demarest bait stations are formed not as gaps in or between walls rising from a base, but instead are holes or openings formed in the shell portion of the cover.
The cover of a bait station such as that disclosed in the above three Demarest patents must be capable of bearing a certain amount of top loading without being crushed. Thin walls for the shell are desirable in order to reduce the amount of plastic used in manufacturing, and thus reduce the cost of the bait station. However, thinning the walls of the shell reduces their strength and crush resistance. In order to provide support for the cover, the above three Demarest patents utilize a plurality of upstanding supporting towers extending from the base and located around the bait well. These upstanding towers not only provide crush resistance for the cover, but they interact with the cover to align it to the base during assembly. In addition, these upstanding towers create multiple internal chambers to direct and orient an insect to the bait area once it enters the interior of the bait station.
During use, it is also important to retain the bait in the central well. Otherwise, during handling, the bait may become dislodged from the well which could defeat the overall efficacy of the bait station. One approach to retaining bait is disclosed in Gentile U.S. Pat. No. 4,793,093. This patent illustrates an insect bait station formed of thin plastic material having a base with a central well for receiving bait, and a cover which includes a depending cup-like member which projects inwardly against the top surface of the bait to aid in holding the bait in the central well. The depending cup-like member, however, does not provide any crush resistance since it bears directly against the bait in the well. Instead, crush resistance is provided by sidewalls which rest upon the top surface of a peripheral wall formed by the base. Another patent illustrating a similar retaining mechanism is Wefler U.S. Pat. No. 5,548,922. Wefler illustrates a recessed portion in the cover that includes a hollow pillar which holds a wick in position in the central well of the base so that insects have access to liquid bait presented by the wick. Again, however, the central pillar does not provide any support for the cover, but merely holds the wick in position.
S. C. Johnson & Son, Inc. has sold in the United States two crawling insect bait stations having divided bait wells. The first, sold as Raid® Double Control Ant Baits, is a bait station comparable to the bait station shown in FIGS. 1 and 2 of Demarest, U.S. Pat. No. 4,837,969, except that the well 18 is somewhat enlarged and a divider meanders across the well 18, dividing it into two subsections, each of which contains a bait differing from the bait in the other subsection. The cover 30 has a central depression that approaches and under finger pressure touches the divider, serving to help retain the bait in the subsections. However, the central depression does not reach or contact the edges of the bait well 18.
The second S. C. Johnson & Son, Inc. bait station referred to has been sold as Raid® Double Control Small Roach Baits, a bait station comparable to the bait station shown in FIGS. 1 and 2 of Demarest, U.S. Pat. No. 5,960,585, except that a divider extends across the bait cup 16, parallel to the longitudinal axis of the bait station, dividing it into two subsections, each of which contains a bait differing from the bait in the other subsection. However, no portion of the cover 14 contacts the bait cup wall 20, the cover 14 being supported by other means.
An ongoing need still exists in the art for a bait station for crawling insects that utilizes a cover made of thin plastic material that spans a base, yet is provided with adequate strength and crush resistance while at the same time aids in bait retention.